Apparatus and method for providing service in wireless communication system

ABSTRACT

An access point (AP) in a wireless communication system supporting a vehicle to infrastructure (V2I) scheme is provided. The AP includes a controller configured to generate a neighbor AP information message including location information of each of neighbor APs and a transmitter configured to transmit the neighbor AP information message. The neighbor AP information message includes a field indicating that a type of a currently transmitted message includes location information, a length field indicating a length of fields located after the length field in the currently transmitted message, and a location information field indicating location information of each of the neighbor Aps.

PRIORITY

This application is a Divisional Application of U.S. patent applicationSer. No. 15/895,505, which was filed on Feb. 13, 2018, and claimspriority under 35 U.S.C. § 119(a) to a Korean Patent Application filedin the Korean Intellectual Property Office on Feb. 13, 2017 and assignedSerial No. 10-2017-0019646, the content of each of which is incorporatedherein by reference.

BACKGROUND 1. Field of the Disclosure

The present disclosure relates generally to an apparatus and method forproviding a service in a wireless communication system, and moreparticularly, to an apparatus and method for providing a service in awireless communication system supporting a vehicle to infrastructure(V2I) scheme.

2. Description of the Related Art

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the internetthe internet of things (IoT) where distributed entities, such as things,exchange and process information without human intervention. Theinternet of everything (IoE), which is a combination of the IoTtechnology and the big data processing technology through connectionwith a cloud server, has emerged.

As technology elements, such as sensing technology, wired/wirelesscommunication and network infrastructure, service interface technology,and security technology have been demanded for IoT implementation, asensor network, a machine-to-machine (M2M) communication, machine typecommunication (MTC), and so forth have been recently researched.

Such an IoT environment may provide intelligent Internet technologyservices that create a new value to human life by collecting andanalyzing data generated among connected things. IoT may be applied to avariety of fields including smart home, smart building, smart city,smart car or connected cars, smart grid, health care, smart appliancesand advanced medical services through convergence and combinationbetween existing information technology (IT) and various industrialapplications.

Generally, in a V2I scheme, a vehicle is accessed to an infrastructureincluding a server, through a wireless communication, so a communicationbetween a station (STA) located at the vehicle and a service may besupported. For example, in the V2I scheme, a wireless communicationbetween a vehicle and an access point (AP) such as a road side unit(RSU) deployed at a road side is supported.

The V2I scheme has been used for a vehicle to provide a multimediaservice, a vehicle management system, an infotainment service such as abanking service, and the like.

FIG. 1 illustrates a structure of a wireless communication systemsupporting a conventional V2I scheme.

Referring to FIG. 1, the wireless communication system includes a server111, a plurality of RSUs, e.g., RSU 1 121, RSU 2 122, and RSU 3 123, anda plurality of STAs, e.g., a STA 1 131 and a STA 2 132. Each of STA 1131 and STA 2 132 may be mounted on a vehicle, or located inside oroutside of the vehicle.

STA 1 131 communicates with RSU 2 122 based on a V2I scheme, andcommunicates with STA 2 132 based on a vehicle-to-vehicle (V2V) scheme.

RSU 1 121, RSU 2 122, and RSU 3 123 use different frequencies. That is,RSU 1 121 uses a frequency 1, RSU 2 122 uses a frequency 2, and RSU 3123 uses a frequency 3.

An infotainment service has been rapidly developed, causing a need inthe V2I scheme for a Wi-Fi based-RSU in which traffic load is easilydistributed and which may be implemented at a relatively low cost.

The V2I scheme needs to provide a service to a moving vehicle, whichrenders handoff as an important issue in the V2I scheme. Since a servicecoverage radius of RSU is relatively small, a vehicle frequently movesamong RSUs and service delay and resource waste due to a handoffregularly occurs.

Accordingly, there is a need in the art for providing a service suchthat a vehicle may perform an effective handoff in a wirelesscommunication system supporting a V2I scheme.

SUMMARY

An aspect of the present disclosure is to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide an apparatus and method for providing a servicein a wireless communication system supporting a V2I scheme.

Another aspect of the present disclosure is to provide an apparatus andmethod for providing a service thereby performing an effective handoffin a wireless communication system supporting a V2I scheme.

Another aspect of the present disclosure is to provide an apparatus andmethod for providing a service thereby decreasing a handoff frequency ina wireless communication system supporting a V2I scheme.

Another aspect of the present disclosure is to provide an apparatus andmethod for providing a service thereby decreasing a time required for ahandoff in a wireless communication system supporting a V2I scheme.

Another aspect of the present disclosure is to provide an apparatus andmethod for providing a service thereby decreasing collision amongacknowledgement (ACK) messages when a plurality of RSUs use the samebasic service set identifier (BSSID) in a wireless communication systemsupporting a V2I scheme.

Another aspect of the present disclosure is to provide an apparatus andmethod for providing a service based on at least one of locationinformation of at least one RSU and location information of a vehicle ina wireless communication system supporting a V2I scheme.

Another aspect of the present disclosure is to provide an apparatus andmethod for providing a service thereby decreasing RSUs to be scanned ina wireless communication system supporting a V2I scheme.

In accordance with an aspect of the present disclosure, an operatingmethod of an access point (AP) in a wireless communication systemsupporting a V2I scheme includes generating a neighbor AP informationmessage including location information of each of neighbor APs, andtransmitting the neighbor AP information message, wherein the neighborAP information message includes a field indicating that a type of acurrently transmitted message includes location information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of each of the neighbor APs.

In accordance with another aspect of the present disclosure, anoperating method of a station (STA) in a wireless communication systemsupporting a V2I scheme, includes generating a neighbor AP informationrequest message including location information of the STA, andtransmitting the neighbor AP information request message to an AP,wherein the neighbor AP information request message includes a fieldindicating that a type of a currently transmitted message includeslocation information, a length field indicating a length of fieldslocated after the length field in the currently transmitted message, anda location information field indicating location information of the STA.

In accordance with another aspect of the present disclosure, anoperating method of an AP in a wireless communication system supportinga V2I scheme includes generating a neighbor AP information messageincluding location information of each of neighbor APs, and transmittingthe neighbor AP information message, wherein the neighbor AP informationmessage includes a location information header field and locationinformation fields indicating location information of the neighbor APs,and wherein the location information header field includes informationrelated to a number of the location information fields and a length ofeach of the location information fields.

In accordance with another aspect of the present disclosure, anoperating method of a STA in a wireless communication system supportinga V2I scheme includes generating a neighbor AP information requestmessage including location information of the STA, and transmitting theneighbor AP information request message to an AP, wherein the neighborAP information request message includes an identifier indicating that acurrently transmitted message requests neighbor AP information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of the STA.

In accordance with another aspect of the present disclosure, anoperating method of a STA in a wireless communication system supportinga V2I scheme includes receiving a neighbor AP information messageincluding location information of neighbor APs from an AP, selectingneighbor APs to be scanned by the STA among the neighbor APs based onthe location information of the neighbor APs, and performing a scanprocess on the selected neighbor APs, wherein the neighbor APinformation message includes a field indicating that a type of acurrently transmitted message includes location information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of each of the neighbor APs.

In accordance with another aspect of the present disclosure, an AP in awireless communication system supporting a V2I) scheme includes acontroller configured to generate a neighbor AP information messageincluding location information of each of neighbor APs, and atransmitter configured to transmit the neighbor AP information message,wherein the neighbor AP information message includes a field indicatingthat a type of a currently transmitted message includes locationinformation, a length field indicating a length of fields located afterthe length field in the currently transmitted message, and a locationinformation field indicating location information of each of theneighbor APs.

In accordance with another aspect of the present disclosure, a STA in awireless communication system supporting a V2I scheme includes acontroller configured to generate a neighbor AP information requestmessage including location information of the STA, and a transmitterconfigured to transmit the neighbor AP information request message to anAP, wherein the neighbor AP information request message includes a fieldindicating that a type of a currently transmitted message includeslocation information, a length field indicating a length of fieldslocated after the length field in the currently transmitted message, anda location information field indicating location information of the STA.

In accordance with another aspect of the present disclosure, an AP in awireless communication system supporting a V2I scheme includes acontroller configured to generate a neighbor AP information messageincluding location information of each of neighbor APs, and atransmitter configured to transmit the neighbor AP information message,wherein the neighbor AP information message includes a locationinformation header field and location information fields indicatinglocation information of the neighbor APs, and wherein the locationinformation header field includes information related to a number of thelocation information fields and a length of each of the locationinformation fields.

In accordance with another aspect of the present disclosure, a STA in awireless communication system supporting a V2I scheme includes acontroller configured to generate a neighbor AP information requestmessage including location information of the STA, and a transmitterconfigured to transmit the neighbor AP information request message to anAP, wherein the neighbor AP information request message includes anidentifier indicating that a currently transmitted message requestsneighbor AP information, a length field indicating a length of fieldslocated after the length field in the currently transmitted message, anda location information field indicating location information of the STA.

In accordance with another aspect of the present disclosure, a STA in awireless communication system supporting a V2I scheme includes atransmitter; a receiver configured to receive a neighbor AP informationmessage including location information of neighbor APs from an AP, and acontroller configure to select neighbor APs to be scanned by the STAamong the neighbor APs based on the location information of the neighborAPs, wherein the transmitter and the receiver are configured to performa scan process on the selected neighbor APs, and wherein the neighbor APinformation message includes a field indicating that a type of acurrently transmitted message includes location information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of each of the neighbor APs.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a structure of a wireless communication systemsupporting a conventional V2I scheme;

FIG. 2 illustrates an example of a handoff process in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 3 illustrates another example of a handoff process in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 4 illustrates a collision issue of an ACK message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 5 illustrates a hidden-terminal issue in a wireless communicationsystem supporting a V2I scheme according to an embodiment of the presentdisclosure;

FIG. 6 illustrates another example of a handoff process in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 7 illustrates a process of providing location information of an RSUand a STA in a wireless communication system supporting a V2I schemeaccording to an embodiment of the present disclosure;

FIG. 8 illustrates an example of a format of a neighbor RSU informationmessage in a wireless communication system supporting a V2I schemeaccording to an embodiment of the present disclosure;

FIG. 9 illustrates an example of a format of a location field includedin a neighbor RSU information message or a request message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 10 illustrates another example of a format of a neighbor RSUinformation message in a wireless communication system supporting a V2Ischeme according to an embodiment of the present disclosure;

FIG. 11 illustrates a format of a location information header fieldincluded in a neighbor RSU information message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 12 illustrates an example of a format of a location informationfield included in a neighbor RSU information message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure;

FIG. 13 illustrates another example of a format of a locationinformation field included in a neighbor RSU information message in awireless communication system supporting a V2I scheme according to anembodiment of the present disclosure;

FIG. 14 illustrates an example of a format of a neighbor AP informationrequest message in a wireless communication system supporting a V2Ischeme according to an embodiment of the present disclosure;

FIG. 15 illustrates an example of a process of performing a scan processin a STA in a wireless communication system supporting a V2I schemeaccording to an embodiment of the present disclosure;

FIG. 16 illustrates another example of a process of performing a scanprocess in a STA in a wireless communication system supporting a V2Ischeme according to an embodiment of the present disclosure;

FIG. 17 illustrates a process of transmitting an ACK message in an RSUin a wireless communication system supporting a V2I scheme according toan embodiment of the present disclosure;

FIG. 18 illustrates an inner structure of an RSU in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure; and

FIG. 19 illustrates an inner structure of a STA in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of embodiments ofthe present disclosure, including various specific details of examplesto assist in that understanding. Accordingly, those of ordinary skill inthe art will recognize that various changes and modifications of theembodiments described herein can be made without departing from thescope and spirit of the present disclosure. In addition, descriptions ofwell-known functions and constructions may be omitted for the sake ofclarity and conciseness.

The terms and words used in the following description and claims are notlimited to their dictionary meanings, but are merely used to enable aclear and consistent understanding of the present disclosure.Accordingly, it should be apparent to those skilled in the art that thefollowing description of embodiments of the present disclosure isprovided for illustration purposes only and not for limiting the presentdisclosure.

It is to be understood that the singular terms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus reference to “a component surface” includes reference to one ormore of such surfaces.

Although ordinal numbers such as “first” and “second” will be used todescribe various components, those components are not limited herein.The terms are used only for distinguishing one component from anothercomponent. For example, a first component may be referred to as a secondcomponent and likewise, a second component may also be referred to as afirst component, without departing from the scope of the presentdisclosure. The expression “and/or” used herein includes any and allcombinations of one or more of the associated listed items.

The terms “include” and “comprise,” as well as derivatives thereof,indicate inclusion without limitation, “or,” is inclusive, meaningand/or, the phrases “associated with” and “associated therewith” as wellas derivatives thereof, may indicate to include, be included within,interconnect with, contain, be contained within, connect to or with,couple to or with, be communicable with, cooperate with, interleave,juxtapose, be proximate to, be bound to or with, have, and have aproperty of, and “controller” indicates any device, system or partthereof that controls at least one operation, and such a device may beimplemented in hardware, firmware or software, or some combination of atleast two of the same.

It should be noted that the functionality associated with any particularcontroller may be centralized or distributed, whether locally orremotely. Definitions for certain words and phrases are providedthroughout this specification, and those of ordinary skill in the artshould understand that in many, if not most instances, such definitionsapply to prior, as well as future uses of such defined words andphrases.

The terminology used herein is for the purpose of describing embodimentsonly and is not intended to be limiting. As used herein, the singularforms are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises” and “has,” when used in this specification,specify the presence of a stated feature, number, step, operation,component, element, or combination thereof, but do not preclude thepresence or addition of one or more other features, numbers, steps,operations, components, elements, or combinations thereof.

The terms used herein, including technical and scientific terms, havethe same meanings as terms that are generally understood by thoseskilled in the art, as long as the terms are not differently defined. Itshould be understood that terms defined in a generally-used dictionaryhave meanings coinciding with those of terms in the related technology.

According to embodiments of the present disclosure, an electronic devicemay include a communication functionality, and may be a smart phone, atablet personal computer (PC), a mobile phone, a video phone, an e-bookreader, a desktop PC, a laptop PC, a netbook PC, a personal digitalassistant (PDA), a portable multimedia player (PMP), an mp3 player, amobile medical device, a camera, and a wearable device, such as ahead-mounted device (HMD), electronic clothes, electronic braces, anelectronic necklace, an electronic appcessory, an electronic tattoo, ora smart watch.

An electronic device may be a smart home appliance with communicationfunctionality, such as a television, a digital video disk (DVD) player,an audio, a refrigerator, an air conditioner, a vacuum cleaner, an oven,a microwave oven, a washer, a dryer, an air purifier, a set-top box, aTV box, such as Samsung HomeSync™, Apple TV™, or Google TV™, a gamingconsole, an electronic dictionary, an electronic key, a camcorder, andan electronic picture frame.

An electronic device may be a medical device, such as magnetic resonanceangiography (MRA) device, a magnetic resonance imaging (MRI) device,computed tomography (CT) device, an imaging device, or an ultrasonicdevice, a navigation device, a global positioning system (GPS) receiver,an event data recorder (EDR), a flight data recorder (FDR), anautomotive infotainment device, a naval electronic device, such as navalnavigation device, gyroscope, or compass, an avionic electronic device,a security device, and an industrial or consumer robot.

An electronic device may be furniture, part of a building/structure, anelectronic board, electronic signature receiving device, a projector,and various measuring devices, such as water, electricity, gas orelectro-magnetic wave measuring devices that include communicationfunctionality.

An electronic device may be any combination of the foregoing devices,but is not limited to the foregoing devices.

A signal transmitting apparatus or a signal receiving apparatus may be astation (STA) and interchangeable with a transmitting apparatus, asignal receiving apparatus may be interchangeable with a receivingapparatus, and the STA may be interchangeable with a mobile station(MS), user equipment (UE), device, or subscriber station.

A signal transmitting apparatus or a signal receiving apparatus may be aroad side unit (RSU), which may be interchangeable with a node B,evolved node B (eNB), AP, or base station (BS).

Embodiments of the present disclosure disclose an apparatus and methodin a wireless communication system supporting a V2I scheme, forproviding a service thereby performing an effective handoff, decreasinga handoff frequency, decreasing a time required for a handoff, anddecreasing collision among ACK messages when a plurality of RSUs use thesame BSSID.

An embodiment of the present disclosure discloses an apparatus andmethod for providing a service in a wireless communication systemsupporting a V2I scheme, based on at least one of location informationof at least one RSU and of a vehicle, and for decreasing RSUs to bescanned.

An apparatus and method disclosed in embodiments of the presentdisclosure may be applied to various communication systems, such as along term evolution (LTE) mobile communication system, an LTE-advanced(LTE-A) mobile communication system, a licensed-assisted access(LAA)-LTE mobile communication system, a high speed downlink packetaccess (HSDPA) mobile communication system, a high speed uplink packetaccess (HSUPA) mobile communication system, a high rate packet data(HRPD) mobile communication system in 3^(rd) generation partnershipproject 2 (3GPP2), a wideband code division multiple access (WCDMA)mobile communication system in 3GPP2, a code division multiple access(CDMA) mobile communication system in 3GPP2, an Institute of Electricaland Electronics Engineers (IEEE) 802.16m communication system, an IEEE802.16e communication system, an evolved packet system (EPS), and amobile internet protocol (mobile IP) system, a digital video broadcastsystem, such as a mobile broadcast service including a digitalmultimedia broadcasting (DMB) service, a digital videobroadcasting-handheld (DVP-H), an advanced television systemscommittee-mobile/handheld (ATSC-M/H) service, and an internet protocoltelevision (IPTV), and a moving picture experts group (MPEG) mediatransport (MMT) system.

In an embodiment of the present disclosure, it will be assumed that awireless communication system supports a V2I scheme based on at leastone of an Optimized Connectivity Experience (OCE) standard of Wi-FiAlliance® Technical Task Group and an IEEE 802.11ai standard, or may bebased on other standard as well as an OCE standard of Wi-Fi Alliance®Technical Task Group and an IEEE 802.11ai standard.

FIG. 2 illustrates an example of a handoff process in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 2, it will be assumed that the wireless communicationsystem supports a V2I scheme which is based on a Wi-Fi scheme supportinga plurality of channels, e.g., 39 channels including 13 2.4 GHz channelsand 26 5 GHz channels. A scan time required per channel may be 60 ms,but is not limited thereto.

When a STA performs a handoff process due to a change in RSU, a channelscan time of 2.34 seconds (39×60 ms) is required. If RSU deploymentdensity is increased for enhancing a service coverage, a handoff countis increased. As a speed of a vehicle at which the STA is locatedincreases, the handoff count increases.

A handoff process when a STA 211 moves through three RSUs, e.g., RSU 1221, RSU 2 222, and RSU 3 223 is illustrated in FIG. 3. It will beassumed that a service coverage radius of each of RSU 1 221, RSU 2 222,and RSU 3 223 is 50 m, and that RSUs use a frequency 1, a frequency 2,and a frequency 3, respectively. A handoff process in FIG. 2 is ahandoff process when STA 211 moves at a speed of 100 km/h, i.e., whenSTA 211 moves about 27.8 meters per second. In this case, STA 211 needsto perform two handoff processes due to a change in RSU, so a channelscan time of 4.68 seconds (2×39×60 ms) is required.

In this case, service quality of a service provided by the wirelesscommunication system is degraded due to the channel scan time of 4.68seconds. So, if a speed of a vehicle and RSU density are relativelyhigh, a handoff process in which all channels are scanned degradesservice quality of the wireless communication system.

FIG. 3 illustrates another example of a handoff process in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 3, it will be assumed that the wireless communicationsystem supports a V2I scheme which is based on a Wi-Fi scheme supportinga plurality of channels, e.g., 39 channels including 13 2.4 GHz channelsand 26 5 GHz channels. A scan time required per channel may be 60 ms.

When a STA performs a handoff process due to a change in RSU, a channelscan time of 2.34 seconds (39×60 ms) is required. If RSU deploymentdensity is increased for enhancing a service coverage, a handoff countis increased. As a speed of a vehicle at which the STA is locatedincreases, the handoff count increases.

A handoff process when a STA 311 moves through five RSUs, e.g., RSU 1321, RSU 2 322, RSU 3 323, RSU 4 324, and RSU 5 325 is illustrated inFIG. 3. It will be assumed that a service coverage radius of each RSU is50 m. A service coverage radius of RSU 4 324 is less than the servicecoverage radius of each of RSU 1 321, RSU 2 322, RSU 3 323, and RSU 5325.

A handoff process in FIG. 3 is when STA 311 moves at a speed of 100km/h, i.e., when STA 311 moves about 27.8 meters per second. In thiscase, STA 311 needs to perform four handoff processes due to a change inan RSU.

However, each RSU has a sizeable service coverage radius, so a handoffcount in the handoff process in FIG. 3 is decreased compared with ahandoff count in the handoff process in FIG. 2. That is, it will beunderstood that a service coverage radius of each RSU is increased tentimes compared to a handoff process in FIG. 2, thereby decreasing ahandoff count.

Nevertheless, a vehicle moving at a high rate of speed causes handoff tofrequently occur, thereby decreasing service quality of a serviceprovided by the wireless communication system. Specifically, when an RSUis not intentionally deployed near a road, or there are numerous privateRSUs in an area, a handoff frequently occurs.

So, even though an RSU service coverage radius is increased, a handoffprocess in which all channels are scanned degrades service quality ofthe wireless communication system if a speed of a vehicle is relativelyhigh and RSU density is relatively high.

FIG. 4 illustrates a collision issue of an ACK message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 4, it will be assumed that the wireless communicationsystem supports a V2I scheme including a plurality of channels and scantime as described above in FIG. 2. In the wireless communication system,as RSU deployment density increases, the handoff count increases.

To prevent degradation of service quality due to a handoff process, thewireless communication system identically sets BSSIDs and frequencies ofRSUs, and a handoff does not occur. That is, when RSUs use the sameBSSID and the same frequency, even though the RSU is changed, thechanged RSU is determined as the same RSU, so a STA does not need toperform a handoff process and a scan operation.

In this case, a plurality of RSUs receive data of a STA, which increasestotal load of the wireless communication system. Each of the pluralityof RSUs transmits an ACK message to the data received from the STA, socollision among the ACK messages may occur.

FIG. 4 illustrates when collision among ACK messages occurs when a STA411 moves through two RSUs, e.g., RSU 1 421 and RSU 2 422 is illustratedin FIG. 4. That is, RSU 1 421 and RSU 2 422 use the same BSSID and thesame frequency, so RSU 1 421 and RSU 2 422 receive (RX) data transmittedby the STA 411 and transmit (TX) an ACK message to the data receivedfrom the STA 411 through the same channel.

The ACK messages transmitted by RSU 1 421 and RSU 2 422 through the samechannel collide, so the STA 411 may not receive the ACK messages to thetransmitted data.

FIG. 5 illustrates a hidden-terminal issue in a wireless communicationsystem supporting a V2I scheme according to an embodiment of the presentdisclosure.

Referring to FIG. 5, typical issues which may occur in the wirelesscommunication system supporting the V2I scheme are a hidden-terminalissue and an exposed-terminal issue. The hidden-terminal issue occurssince a STA transmits data to an RSU while another STA transmits data tothe RSU. That is, a transmission collision issue which occurs since theSTA and the other STA do not exist within a range in which the STA andthe other STA may detect a transmission state each other is thehidden-terminal issue. As a service coverage of RSUs which use the samefrequency increases, the more serious the hidden-terminal issue becomes.That is, as described in FIG. 4, in the wireless communication systemsupporting the V2I scheme, a handoff does not occur by setting BSSIDsand frequencies of RSUs the same for preventing service qualitydegradation due to a handoff process. In this case, the hidden-terminalissue may occur.

For example, in FIG. 5, a hidden-terminal issue may occur since a STA 2512 transmits data to RSU 1 521 while a STA 1 511 transmits data to RSU1 521. That is, if STA 1 511 and STA 2 512 do not exist within a rangein which STA 1 511 and STA 2 512 may detect transmission each other andSTA 1 511 and STA 2 512 transmit data using the same frequency, datatransmitted by STA 1 511 and data transmitted by STA 2 512 collide.

In FIG. 5, a hidden-terminal issue may occur since STA 3 513 transmitsdata to RSU 2 522 while STA 2 512 transmits data to RSU 2 522. That is,if STA 2 512 and STA 3 513 do not exist within a range in which STA 2512 and STA 3 513 may detect transmission each other and STA 2 512 andSTA 3 513 transmit data using the same frequency, data transmitted bySTA 2 512 and data transmitted by STA 3 513 collide.

As the number of vehicles which move at a low speed increases, the moreserious the above-described hidden-terminal issue becomes.

FIG. 6 illustrates another example of a handoff process in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 6, it will be assumed that the wireless communicationsystem supports a V2I scheme which is based on a Wi-Fi scheme supportinga plurality of channels and scan time as described above in FIG. 2.

When a STA performs a handoff process due to a change in RSU, a channelscan time of 2.34 seconds (39×60 ms) is required. In the wirelesscommunication system, if RSU deployment density is increased forenhancing a service coverage, a handoff count is increased. As a speedof a vehicle at which the STA is located increases, the handoff countincreases.

So, an embodiment of the present disclosure discloses a handoff processwhich is based on an IEEE 802.11ai standard.

An AP (or RSU) may decrease a scan time of STAs which have accessed theAP by providing a message including information on neighbor APs of theAP, e.g., a reduced neighbor report (RNR) message, which may betransmitted through at least one of beacon frames, probe responseframes, and fast initial link setup (FILS) discovery frames. A beaconframe, a probe response frame, and an FILS discovery frame have beendefined in an IEEE 802.11ai standard, and thus, a detailed descriptionthereof will be omitted herein.

The RNR message includes at least one of channel information, beacontiming information and service set identifier (SSID) information foreach AP.

Upon receiving the RNR message transmitted by the AP, the STA sets achannel for which an AP that the STA may access exists to a scan targetand performs a scan process. So, even though the STA needs to performhandoff processes in the manner of the handoff process in FIG. 2, theSTA decreases a time required for performing a scan process to decreasea time required for a handoff process.

Referring to FIG. 6, each of a plurality of APs, i.e., RSU 1 611, RSU 2612, RSU 3 613, and RSU 614 transmits (TX) an RNR message to a STA 621,which detects neighbor RSU information and channel information for eachof RSU 1 611, RSU 2 612, RSU 3 613, and RSU 614. In FIG. 6, it will beassumed that RSU 1 611, RSU 2 612, RSU 3 613, and RSU 4 614 usefrequency 1, frequency 4, frequency 2, and frequency 3, respectively.

However, a handoff process using an RNR message which is based on theIEEE 802.11ai standard considers low speed-movement such as a stop andwalking, so even though the STA 621 receives (RX) the neighbor RSUinformation for each of RSU 1 611, RSU 2 612, RSU 3 613, and RSU 4 614,the STA 621 may not select and scan the RSU related to a mobility of theSTA 621. That is, the handoff process using the RNR message which isbased on the IEEE 802.11ai standard has not disclosed detecting anoptimal RSU based on a speed of a vehicle, so a STA which receives anRNR needs to scan all RSUs which correspond to neighbor RSU informationincluded in the RNR message.

In the handoff process using the RNR message which is based on the IEEE802.11ai standard, a scan process is performed based on a beacon frame,which compromises decreasing a time required for performing a handoffprocess.

So, an embodiment of the present disclosure discloses decreasing arelatively long handoff time occurred due to a time required forperforming a scan process in a STA in a Wi-Fi network environment whereRSUs use different BSSIDs and different frequencies, providing RSUlocation information for effective scan/channel selection, an effectivescan scheme, a channel selecting scheme of decreasing a time requiredfor performing a handoff process, solving an ACK message collision issuewhich may occur when RSUs use the same BSSID and the same frequency, andtransmitting an ACK message in a specific RSU among a plurality of RSUs.

That is, an embodiment of the present disclosure discloses providingneighbor RSU information, e.g., channel information of a neighbor RSU,information related to a beacon transmission time, SSID information, RSUlocation information, providing neighbor RSU information based on a STArequest, an effective channel scan scheme, and a channel selectingscheme of decreasing a time required for performing a handoff process ina Wi-Fi network environment where RSUs use different BSSIDs anddifferent frequencies, and determining whether to transmit an ACKmessage based on location information of a STA and transmitting the ACKmessage based on the determined result in RSU when RSUs use the sameBSSID and the same frequency.

FIG. 7 illustrates a process of providing location information of an RSUand a STA in a wireless communication system supporting a V2I schemeaccording to an embodiment of the present disclosure.

Referring to FIG. 7, each of RSU 1 711, RSU 2 712, RSU 3 713, and RSU714 transmits a neighbor RSU information message including neighbor RSUinformation for each of neighbor RSUs. The neighbor RSU informationmessage may be implemented with various formats, one of which will bedescribed below, and a detailed description thereof will be omittedherein.

A STA 721 may receive the neighbor RSU information message transmittedby each of RSU 1 711, RSU 2 712, RSU 3 713, and RSU 4 714 and detect theneighbor RSU information for each of the RSUs. In FIG. 7, it will beassumed that RSU 1 711, RSU 2 712, RSU 3 713, and RSU 4 714 usefrequency 1, frequency 4, frequency 2, and frequency 3, respectively.

STA 721 transmits a request message including location information ofSTA 721. Each of RSU 1 711, RSU 2 712, RSU 3 713, and RSU 714 receivesthe request message transmitted by the STA 721, and may determinewhether to transmit a neighbor RSU information message based on thelocation information of the STA 721 included in the request message. Therequest message may be implemented with various formats, one of whichwill be described below, and a detailed description thereof will beomitted herein.

FIG. 8 illustrates an example of a format of a neighbor RSU informationmessage in a wireless communication system supporting a V2I schemeaccording to an embodiment of the present disclosure.

Referring to FIG. 8, a neighbor RSU information message includes anelement identifier (ID) field, a length field, and n neighbor RSUinformation fields, i.e., neighbor RSU information field #1, neighborRSU information field #2, . . . , neighbor RSU information field #n.

The element ID field may be implemented with one octet, and the lengthfield may be implemented with one octet, but the present disclosure isnot limited thereto. A size of each of neighbor RSU information field#1, neighbor RSU information field #2, . . . , and neighbor RSUinformation field #n may vary.

Each of the neighbor RSU information fields includes a location fieldincluding value pairs identifying location information of APs, and asize of each of the neighbor RSU information fields may vary. Thelocation field will be described with reference to FIG. 9, and adetailed description thereof will be omitted herein.

FIG. 9 illustrates an example of a format of a location field includedin a neighbor RSU information message or a request message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 9, it will be noted that a format of a location fieldincluded in a neighbor RSU information message or a request message inFIG. 9 is a format of a location field included in a neighbor RSUinformation message or a request message when the wireless communicationsystem supports a V2I scheme which is based on an OCE standard.

A neighbor RSU information message used for transmitting locationinformation of neighbor APs in an AP will be described below.

When the neighbor AP information message includes location informationof neighbor APs, a format of the neighbor AP information message may beexpressed as shown below in Table 1. For example, the neighbor APinformation message may be implemented with a location indicationattribute.

TABLE 1 Field Name Size (Octets) Value Description Attribute 1 SpecificIdentifies the type of ID Decimal # OCE attribute. Length Specific SizeVariable Length of the following fields in the attribute. LocationVariable Variable A field that is a sequence of length and value pairsthat identify the locations of APs (AP->STA).

As shown in Table 1, the neighbor AP information message includes anattribute ID field, a length field, and a location field.

The attribute ID field is used for identifying a type of an attribute,i.e., an OCE attribute, and may be implemented with one octet. The OCEattribute in Table 1 is a location indication attribute, so it will beidentified that the OCE attribute is the location indication attributethrough the attribute ID field.

The length field is used for indicating a length of fields after thelength field in the attribute, i.e., the OCE attribute, and may beimplemented with a specific size.

The location field includes value pairs identifying location informationof APs, and a size of the location field may vary. The location fieldwill be described with reference to FIG. 9, and a detailed descriptionthereof will be omitted herein.

If the neighbor AP information message includes at least one ofdirection information and speed information of a STA as well as locationinformation of neighbor APs, a format of the neighbor AP informationmessage may be expressed as shown below in Table 2. For example, theneighbor AP information message may be implemented with alocation/direction/velocity (LDV) indication attribute.

TABLE 2 Field Name Size (Octets) Value Description Attribute 1 SpecificIdentifies the type of ID Decimal # OCE attribute. Length Specific SizeVariable Length of the following fields in the attribute. LocationVariable Variable A field that is a sequence of length and value pairsthat identify the locations of APs. Direction 0 or 1 Variable Anoptional field Length used if a direction of vehicle is used DirectionSpecific Size Variable An optional field that is a value to identify themoving direction of vehicle Velocity 0 or 1 Variable An optional fieldused Length if a velocity of vehicle is used Velocity Specific SizeVariable An optional field that is a value to identify the velocity ofvehicle

As shown in Table 2, the neighbor AP information message includes anattribute ID field, a length field, a location field, a direction lengthfield, a direction field, a speed length field, and a speed field.

The attribute ID field is used for identifying a type of an attribute,i.e., an OCE attribute, and may be implemented with one octet. The OCEattribute in Table 2 is an LDV indication attribute, so it will beidentified that the OCE attribute is the LDV indication attributethrough the attribute ID field.

The length field is used for indicating a length of fields after thelength field in the attribute, i.e., the OCE attribute, and may beimplemented with a specific size.

The location field includes value pairs identifying location informationof APs, and a size of the location field may vary. The location fieldwill be described with reference to FIG. 9, and a detailed descriptionthereof will be omitted herein.

The direction length field is included in the neighbor AP informationmessage if direction information indicating a direction of a STA whichis mounted on located at the vehicle is used. The direction length fieldis an optional field, and a value of the direction length field may bezero (0) or 1 octet.

The direction field is used for indicating a value identifying a movingdirection of the STA. The direction field may be implemented with aspecific size, and the direction field is an optional field.

The speed length field is included in the neighbor AP informationmessage if speed information indicating a speed of the STA is used, isan optional field, and may have a value of 0 or 1 octet.

The speed field is used for indicating a value identifying a speed ofthe STA, may be implemented with a specific size, and is an optionalfield.

A format of a request message used for a STA to transmit locationinformation of the STA will be described below.

If the request message includes location information of the STA, aformat of the request message may be expressed as shown below in Table3. For example, the request message may be implemented with a locationindication attribute.

TABLE 3 Field Name Size (Octets) Value Description Attribute 1 SpecificIdentifies the type of ID Decimal # OCE attribute. Length SpecificVariable Length of the following Size fields in the attribute. LocationVariable Variable A field that is a sequence of length and a value pairthat identifies the location of vehicle (STA-> AP).

As shown in Table 3, the request message includes an attribute ID field,a length field, and a location field.

The attribute ID field is used for identifying a type of an attribute,i.e., an OCE attribute, and may be implemented with one octet. The OCEattribute in Table 3 is a location indication attribute, so it will beidentified that the OCE attribute is the location indication attributethrough the attribute ID field.

The length field is used for indicating a length of fields after thelength field in the OCE attribute, and may be implemented with aspecific size.

The location field includes a value pair identifying locationinformation of a STA, and a size of the location field may vary. Thelocation field will be described with reference to FIG. 9, and adetailed description thereof will be omitted herein.

If the request message includes at least one of location information,direction information, and speed information of a STA, a format of therequest message may be expressed as shown below in Table 4. For example,the request message may be implemented with an LDV indication attribute.

TABLE 4 Field Name Size (Octets) Value Description Attribute 1 SpecificIdentifies the type of ID Decimal # OCE attribute. Length SpecificVariable Length of the following Size fields in the attribute. LocationVariable Variable A field that is a sequence of length and a value pairthat identifies the location of vehicle. Direction 0 or 1 Variable Anoptional field Length used if a direction of vehicle is used DirectionSpecific Variable An optional field that Size is a value to identify themoving direction of vehicle Velocity 0 or 1 Variable An optional fieldLength used if a velocity of vehicle is used Velocity Specific VariableAn optional field that is Size a value to identify the velocity ofvehicle

As shown in Table 4, the request message includes an attribute ID field,a length field, a location field, a direction length field, a directionfield, a speed length field, and a speed field.

The attribute ID field is used for identifying a type of an attribute,i.e., an OCE attribute, and may be implemented with one octet. The OCEattribute in Table 4 is an LDV indication attribute, so it will beidentified that the OCE attribute is the LDV indication attributethrough the attribute ID field.

The length field is used for indicating a length of fields after thelength field in the OCE attribute, and may be implemented with aspecific size.

The location field includes a value pair identifying locationinformation of a STA, and a size of the location field may vary. Thelocation field will be described with reference to FIG. 9, and adetailed description thereof will be omitted herein.

The direction length field is included in the request message ifdirection information indicating a direction of a STA which is mountedon a vehicle or located at the vehicle is used. The direction lengthfield is an optional field, and has a value of 0 or 1 octet.

The direction field is used for indicating a value identifying a movingdirection of the STA, may be implemented with a specific size, and is anoptional field.

The speed length field is included in the request message if speedinformation indicating a speed of the STA is used. The speed lengthfield is an optional field, and has a value of 0 or 1 octet.

The speed field is used for indicating a value identifying a speed ofthe STA, may be implemented with a specific size, and is an optionalfield.

A format of a location field included in a neighbor AP informationmessage or a request message will be described with reference to FIG. 9.

The location field may include at least one value pair including alength sub-field and a location value sub-field.

The length sub-field is be implemented with one octet and indicateslength of a sub-field after the length sub-field.

A size of the location value sub-field may vary. The location valuesub-field may include at least one of latitude information and longitudeinformation. If the location value sub-field includes both the latitudeinformation and the longitude information, the location value sub-fieldmay be implemented with a format including a sub-field which correspondsto the latitude information and a sub-field which corresponds to thelongitude information.

FIG. 10 illustrates another example of a format of a neighbor RSUinformation message in a wireless communication system supporting a V2Ischeme according to an embodiment of the present disclosure.

Referring to FIG. 10, it will be noted that a format of a neighbor RSUinformation message in FIG. 10 is a neighbor AP information message whenthe wireless communication system supports a V2I scheme which is basedon an IEEE 802.11ai standard.

In FIG. 10, it will be understood that a neighbor AP information messageis implemented with a format which is generated by modifying an RNRmessage used in the IEEE 802.11ai standard, i.e., an RNR element.However, the neighbor AP information message may be implemented withanother element, such as a location field format.

The neighbor AP information message includes a location informationheader field, an operating class field, a channel number field, andlocation information field #1 to location information field #n.

The location information header field may be implemented with 2 octets,and includes a count and location information of location informationfield #1 to location information field #n. The location informationheader field will be described with reference to FIG. 10, and a detaileddescription thereof will be omitted herein.

The operating class field may be implemented with 1 octet, and is usedfor indicating a band and a bandwidth of a channel of an AP whichcorresponds to each of location information field #1 to locationinformation field #n.

The channel number field may be implemented with 1 octet, and is usedfor indicating a last known primary channel of the AP which correspondsto each of location information field #1 to location information field#n.

Each of location information field #1 to location information field #nis used for indicating location information of a neighbor AP whichoperates on a channel, and each will be described with reference to FIG.12. A detailed description thereof will be omitted herein.

FIG. 11 illustrates a format of a location information header fieldincluded in a neighbor RSU information message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 11, it will be noted that a format of a locationinformation header field is a location field format as described in FIG.10.

In FIG. 11, the location information header field includes locationinformation field type sub-field, a reserved sub-field, a locationinformation count sub-field, and a location information lengthsub-field.

The location information field type sub-field may be implemented with 2bits, but is not limited thereto. If a value of the location informationfield type sub-field is 0 (zero), the location information field typesub-field defines a structure of the location information field. Othervalues, e.g., 1, 2, and 3 are reserved for future use.

The reserved sub-field may be implemented with 2 bits, and is reservedfor future use.

The location information count sub-field may be implemented with 4 bits,and indicates a value obtained by subtracting 1 from the number oflocation information fields included in the neighbor AP informationmessage. If a value of the location information count sub-field is 0, itis indicated that one location information field exists.

The location information length sub-field may be implemented with 1octet and indicates length, e.g., octet length of each of locationinformation fields included in the neighbor AP information message.

FIG. 12 illustrates an example of a format of a location informationfield included in a neighbor RSU information message in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 12, it will be noted that a format of a locationinformation field in FIG. 12 is a location field format as described inFIG. 10.

In FIG. 12, the location information field includes a locationsub-field, a BSSID sub-field, and a short-SSID sub-field.

A size of the location sub-field may vary, and the location sub-fieldincludes location information of an AP. The location information of theAP may include at least one of latitude information and longitudeinformation.

The BSSID sub-field indicates a BSSID of the AP, and may be included inthe location information field if necessary. If the BSSID sub-field isincluded in the location information field, the BSSID sub-field may beimplemented with 6 octets. In FIG. 12, “0 or 6 octets” means that alength of the BSSID sub-field is 6 octets if the BSSID sub-field isincluded in the location information field, and that the length of theBSSID sub-field is 0 octets, that is, the BSSID sub-field is notpresent, if the BSSID sub-field is not included in the locationinformation field.

The short-SSID sub-field indicates a short-SSID of the AP, and may beincluded in the location information field if necessary. If theshort-SSID sub-field is included in the location information field, theshort-SSID sub-field may be implemented with 4 octets. In FIG. 12, “0 or4 octets” means that a length of the short-SSID sub-field is 4 octets ifthe short-SSID sub-field is included in the location information field,and that the length of the short-SSID sub-field is 0 octets, that is,the short-SSID sub-field is not present, if the short-SSID sub-field isnot included in the location information field.

FIG. 13 illustrates another example of a format of a locationinformation field included in a neighbor RSU information message in awireless communication system supporting a V2I scheme according to anembodiment of the present disclosure.

Referring to FIG. 13, it will be noted that a format of a locationinformation field is a location field format as described in FIG. 10.

In FIG. 13, the location information field includes a location/latitudesub-field, a location/longitude sub-field, a BSSID sub-field, and ashort-SSID sub-field.

A size of the location/latitude sub-field may be 4 octets but is notlimited thereto, and the location/latitude sub-field includes latitudeinformation of an AP.

A size of the location/longitude sub-field may be 4 octets but is notlimited thereto, and the location/longitude sub-field includes longitudeinformation of the AP.

The BSSID sub-field indicates a BSSID of the AP, and may be included inthe location information field if necessary. If the BSSID sub-field isincluded in the location information field, the BSSID sub-field may beimplemented with 6 octets. In FIG. 13, “0 or 6 octets” means that alength of the BSSID sub-field is 6 octets if the BSSID sub-field isincluded in the location information field, and that the length of theBSSID sub-field is 0 octet, that is, the BSSID sub-field is not present,if the BSSID sub-field is not included in the location informationfield.

The short-SSID sub-field indicates a short-SSID of the AP, and may beincluded in the location information field if necessary. If theshort-SSID sub-field is included in the location information field, theshort-SSID sub-field may be implemented with 4 octets. In FIG. 13, “0 or4 octets” means that a length of the short-SSID sub-field is 4 octets ifthe short-SSID sub-field is included in the location information field,and that the length of the short-SSID sub-field is 0 octet, that is, theshort-SSID sub-field is not present, if the short-SSID sub-field is notincluded in the location information field.

FIG. 14 illustrates an example of a format of a neighbor AP informationrequest message in a wireless communication system supporting a V2Ischeme according to an embodiment of the present disclosure.

Referring to FIG. 14, it will be noted that a format of a neighbor APinformation request message is a neighbor AP information request messagewhen the wireless communication system supports a V2I scheme which isbased on an IEEE 802.11ai standard.

In FIG. 14, the neighbor AP information request message includes anelement ID field, a length field, a location field, a direction field, avelocity field, and an optional information field.

The element ID field may be implemented with one octet, and may includean ID indicating that a corresponding element is for requesting neighborAP information.

The length field indicates length of fields after the length field, andis implemented with one octet.

A size of the location field may vary, and the location field indicateslocation information of a STA.

A size of the direction field may vary, and the direction fieldindicates a moving direction of the STA and is an optional field.

A size of the velocity field may vary, and the velocity field indicatesa speed of the STA and is an optional field.

A size of the optional field may vary, and the optional field mayinclude other information. A detailed description of informationincluded in the optional field will be omitted herein.

FIG. 15 illustrates an example of a process of performing a scan processin a STA in a wireless communication system supporting a V2I schemeaccording to an embodiment of the present disclosure.

Referring to FIG. 15, a STA 1511 receives a neighbor RSU informationmessage from each of RSU 1 1521, RSU 2 1522, RSU 3 1523, RSU 4 1524, andRSU 5 1525, wherein each RSU transmits (TX) a neighbor RSU informationmessage including location information (for example, a neighbor reportfor location (NRL)) for neighbor RSUs of each RSU.

It will be assumed that RSU 1 1521, RSU 2 1522, RSU 3 1523, RSU 4 1524,and RSU 5 1525 use frequency 1, frequency 4, frequency 2, frequency 3,and frequency 5, respectively.

A range of information on neighbor RSUs which each of RSU 1 1521, RSU 21522, RSU 3 1523, RSU 4 1524, and RSU 5 1525 includes in the neighborRSU information, i.e., a range of neighbor RSUs of which locationinformation is included in the neighbor RSU information message, may bedetermined based on various parameters. For example, RSUs of which thelocation information is included in the neighbor RSU information messagemay be located within a preset distance from the RSU which transmits theneighbor RSU information message. The neighbor RSU information messagehas been described above, and a detailed description thereof will beomitted herein.

STA 1511 may select the RSU and a channel to be scanned by STA 1511based on a neighbor RSU information message received from each of RSU 11521, RSU 2 1522, RSU 3 1523, RSU 4 1524, and RSU 5 1525. That is, STA1511 may select the RSU and the channel to be scanned by STA 1511 basedon location information of neighbor RSUs included in the neighbor RSUinformation message received from each of RSU 1 1521, RSU 2 1522, RSU 31523, RSU 4 1524, and RSU 5 1525.

Selecting an RSU and a channel to be scanned by STA 1511 may beimplemented with various forms. For example, STA 1511 may select RSUswhich are located within a distance estimated to have good channelquality, i.e., a distance estimated to satisfy a channel qualitythreshold value as RSUs to be scanned by STA 1511. Channel quality maybe expressed as various forms, such as received signal code power(RSCP), reference signal received power (RSRP), a reference signalstrength indicator (RSSI), reference signal received quality (RSRQ), acarrier-to-interference noise ratio (CINR), a signal-to-noise ratio(SNR), and a block error rate (BLER). In an embodiment of the presentdisclosure, it will be assumed that an RSSI is used as channel quality,so the channel quality threshold value may be an RSSI threshold valuedetermined based on various parameters, and the same RSSI thresholdvalue or a different RSSI threshold value may be set for each RSU.

STA 1511 selects RSUs which are located within the distance estimated tosatisfy the RSSI threshold value as RSUs to be scanned by STA 1511because that a time required for performing a handoff process increasesif an RSSI of a specific RSU does not satisfy the RSSI threshold value.

In FIG. 15, STA 1511 may acquire location information for each of RSU 21522, RSU 3 1523, RSU 4 1524, and RSU 5 1525 based on a neighbor RSUinformation message received from RSU 1 1521, and determine RSU 2 1522,RSU 4 1524, and RSU 5 1525 among RSU 2 1522, RSU 3 1523, RSU 4 1524, andRSU 5 1525 as RSUs to be scanned.

FIG. 16 illustrates another example of a process of performing a scanprocess in a STA in a wireless communication system supporting a V2Ischeme according to an embodiment of the present disclosure.

Referring to FIG. 16, it will be assumed that a STA receives a neighborRSU information message from RSU 1. The neighbor RSU information messagehas been described above, and a detailed description thereof will beomitted herein. It will be assumed that RSU 1 transmits the neighbor RSUmessage including location information of each of RSU 2, RSU 3, RSU 4,and RSU 5. That is, it will be assumed that RSU 2, RSU 3, RSU 4, and RSU5 are neighbor RSUs for RSU 1.

The STA may select the RSU and a channel to be scanned based on theneighbor RSU information message received from RSU 1 and locationinformation, a moving direction, and a moving path of the STA. In FIG.16, it will be assumed that the STA selects RSU 2, RSU 4, and RSU 5 asRSU to be scanned. For example, the STA selects RSUs which are locatedwithin a distance estimated to satisfy an RSSI threshold value as RSUsto be scanned by the STA. Alternatively, the STA may perform a scanprocess for all RSUs included in the neighbor RSU information, orsequentially perform a scan process from the RSU closest in distance tothe STA.

Unless additional information is provided beforehand, the STA needs toreceive a beacon frame and a FILS discovery frame for transmitting aprobe request frame as soon as possible after selecting the channel tobe scanned.

The STA may minimize a time required for a handoff through a schedulingprocess in which the STA is switched to a channel on which a scanprocess will be performed before transmitting the beacon frame and theFILS discovery frame based on information on timing at which the beaconframe is transmitted and the STA will switch the channel

If an RSSI estimation value which is based on the location informationof the STA and the location information of the neighbor RSUs is lessthan an RSSI threshold value when the scheduling process in which thechannel is switched is performed, the STA may perform a schedulingprocess after excluding a channel of which an RSSI estimation value isless than the RSSI threshold value.

FIG. 17 illustrates a process of transmitting an ACK message in an RSUin a wireless communication system supporting a V2I scheme according toan embodiment of the present disclosure.

Referring to FIG. 17, RSU 1 1711 and RSU 2 1712 receive a message ordata transmitted by a STA 1721, and may detect location of STA 1721based on location information included in the message transmitted by STA1721, e.g., a safety message including location information which isbased on a dedicated short-range communication (DSRC) or the datatransmitted by STA 1721.

Each of RSU 1 1711 and RSU 2 1712 may determine whether to transmit anACK message for the safety message or the data received from STA 1721based on the location of STA 1721. For example, each of RSU 1 1711 andRSU 2 1712 detects a distance between STA 1721 and each of RSU 1 1711and RSU 2 1712 based on the location of STA 1721.

Each of RSU 1 1711 and RSU 2 1712 determines whether the detecteddistance between STA 1721 and each of RSU 1 1711 and RSU 2 1712 isgreater than a threshold distance. If the detected distance is greaterthan the threshold distance, a corresponding RSU does not transmit anACK message to the received safety message or data.

In FIG. 17, it will be assumed that a distance between RSU 2 1712 andSTA 1721 is greater than the threshold distance, so RSU 2 1712 does nottransmit an ACK message to the received safety message or data to STA1721.

It will be assumed that a distance between RSU 1 1711 and STA 1721 isless than or equal to the threshold distance, so RSU 1 1711 transmits anACK message to the received safety message or data to STA 1721.

In FIG. 17, it will be assumed that there is one RSU which is locatedwithin the threshold distance from STA 1721. However, if there are aplurality of RSUs which are located within the threshold distance fromSTA 1721, RSU closest to STA 1721 among the plurality of RSUs maytransmit an ACK message to the received safety message or data to STA1721. Specific RSUs may know location information of the specific RSUsin advance through Subnet/Proximity/Profile.

FIG. 18 illustrates an inner structure of RSU in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 18, RSU 1800 includes a transmitter 1811, a controller1813, a receiver 1815, and a storage unit 1817.

The controller 1813 controls the overall operation of RSU 1800. Moreparticularly, the controller 1813 controls an operation related toperforming a handoff process and transmitting an ACK message in thewireless communication system supporting the V2I scheme, as describedabove with reference to FIGS. 2 to 17. Thus, a detailed descriptionthereof will be omitted herein.

The transmitter 1811 transmits various signals and messages to otherdevices, e.g., other RSUs, a STA, or a server included in the wirelesscommunication system under a control of the controller 1813.

The receiver 1815 receives various signals and various messages fromother devices, e.g., other RSUs, a STA, or a server included in thewireless communication under a control of the controller 1813. Thevarious transmitted and received signals and messages have beendescribed above, and a detailed description thereof will be omittedherein.

The storage unit 1817 stores various programs, various data related tothe operation of providing the service in the wireless communicationsystem supporting the V2I scheme, e.g., the operation of performing thehandoff process and transmitting the ACK message performed in RSU 1800under a control of the controller 1813.

The storage unit 1817 stores various signals and various messages whichare received by the receiver 1815 from the other devices.

While the transmitter 1811, the controller 1813, the receiver 1815, andthe storage unit 1817 are described in RSU 1800 as separate units, it isto be understood that this is merely for convenience of description, andtwo or more of the transmitter 1811, the controller 1813, the receiver1815, and the storage unit 1817 may be incorporated into a single unit.

RSU 1800 may be implemented with at least one processor.

FIG. 19 illustrates an inner structure of a STA in a wirelesscommunication system supporting a V2I scheme according to an embodimentof the present disclosure.

Referring to FIG. 19, a STA 1900 includes a transmitter 1911, acontroller 1913, a receiver 1915, and a storage unit 1917.

The controller 1913 controls the overall operation of STA 1900. Moreparticularly, the controller 1913 controls an operation related toperforming a handoff process and transmitting an ACK message, asdescribed with reference to FIGS. 2 to 17. Thus, a detailed descriptionthereof will be omitted herein.

The transmitter 1911 transmits various signals and various messages toother devices, e.g., other STAs or RSU included in the wirelesscommunication system under a control of the controller 1913.

The receiver 1915 receives various signals and various messages fromother devices, e.g., other STAs or RSU included in the wirelesscommunication under a control of the controller 1913. The varioussignals and messages transmitted and received in the receiver 1915 havebeen described above with reference to FIGS. 2 to 17, and a detaileddescription thereof will be omitted herein.

The storage unit 1917 stores various programs, various data related toperforming the handoff process and transmitting the ACK messageperformed in STA 1900 under a control of the controller 1913.

The storage unit 1917 stores various signals and various messages whichare received by the receiver 1915 from the other devices.

While the transmitter 1911, the controller 1913, the receiver 1915, andthe storage unit 1917 are described in STA 1900 as separate units, it isto be understood that this is merely for convenience of description. Inother words, two or more of the transmitter 1911, the controller 1913,the receiver 1915, and the storage unit 1917 may be incorporated into asingle unit.

STA 1900 may be implemented with at least one processor.

In accordance with an aspect of the present disclosure, an operatingmethod of an AP in a wireless communication system supporting a V2Ischeme includes generating a neighbor AP information message includinglocation information of each of neighbor APs, and transmitting theneighbor AP information message, wherein the neighbor AP informationmessage includes a field indicating that a type of a currentlytransmitted message includes location information, a length fieldindicating a length of fields located after the length field in thecurrently transmitted message, and a location information fieldindicating location information of each of the neighbor APs.

The location information field includes a location value sub-fieldincluding at least one of latitude information and longitude informationof one of the neighbor APs, and a length sub-field indicating a lengthof a sub-field located after the length sub-field.

In accordance with an aspect of the present disclosure, an operatingmethod of a STA in a wireless communication system supporting a V2Ischeme includes generating a neighbor AP information request messageincluding location information of the STA, and transmitting the neighborAP information request message to an AP, wherein the neighbor APinformation request message includes a field indicating that a type of acurrently transmitted message includes location information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of the STA.

The location information field includes a length sub-field indicating alength of a sub-field located after the length sub-field, and a locationvalue sub-field including at least one of latitude information andlongitude information of the STA.

The neighbor AP information request message further includes at leastone of direction information indicating a moving direction of the STAand speed information indicating a speed of the STA.

In accordance with an aspect of the present disclosure, an operatingmethod of an AP in a wireless communication system supporting a V2Ischeme includes generating a neighbor AP information message includinglocation information of each of neighbor APs, and transmitting theneighbor AP information message, wherein the neighbor AP informationmessage includes a location information header field and locationinformation fields indicating location information of the neighbor APs,and wherein the location information header field includes informationrelated to a number of the location information fields and a length ofeach of the location information fields.

The neighbor AP information message further includes an operating classfield indicating a channel band and a bandwidth of each of the neighborAPs and a channel number field indicating a last known primary channelof each of the neighbor APs.

Each of the location information fields includes a location sub-fieldincluding at least one of latitude information and longitude informationof one of the neighbor APs further includes, at least one of a BSSIDsub-field indicating a BSSID of one of the neighbor APs, and ashort-SSID field indicating a short-SSID of the AP, a location/latitudesub-field indicating latitude information of one of the neighbor APs,and a location/longitude sub-field indicating longitude information ofthe AP further includes, and at least one of a BSSID sub-fieldindicating a BSSID of one of the neighbor APs, and a short-SSID fieldindicating a short-SSID of the AP.

The information related to the number of the location information fieldsindicates a value obtained by subtracting a preset value from the numberof the location information fields.

In accordance with still another aspect of the present disclosure, anoperating method of a STA in a wireless communication system supportinga V2I scheme includes generating a neighbor AP information requestmessage including location information of the STA, and transmitting theneighbor AP information request message to an AP, wherein the neighborAP information request message includes an identifier indicating that acurrently transmitted message requests neighbor AP information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of the STA.

The location information field includes at least one of latitudeinformation and longitude information of the STA.

The neighbor AP information request message further includes at leastone of direction information indicating a moving direction of the STAand speed information indicating a speed of the STA.

In accordance with still another aspect of the present disclosure, anoperating method of a STA in a wireless communication system supportinga V2I scheme includes receiving a neighbor AP information messageincluding location information of neighbor APs from an AP, selectingneighbor APs to be scanned by the STA among the neighbor APs based onthe location information of the neighbor APs, and performing a scanprocess on the selected neighbor APs, wherein the neighbor APinformation message includes a field indicating that a type of acurrently transmitted message includes location information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of each of the neighbor APs.

The location information field includes a location value sub-fieldincluding at least one of latitude information and longitude informationof one of the neighbor APs, and a length sub-field indicating a lengthof a sub-field located after the length sub-field.

The operating method further includes transmitting a neighbor APinformation request message to the AP, and the neighbor AP informationrequest message includes a field indicating that a type of a currentlytransmitted message includes location information, a length fieldindicating a length of fields located after the length field in thecurrently transmitted message, and a location information fieldindicating location information of the STA.

As is apparent from the foregoing description, embodiments of thepresent disclosure provide a service in a wireless communication systemsupporting a V2I scheme for performing an effective handoff, decreasinga handoff frequency, decreasing a time required for a handoff, anddecreasing collision among ACK messages when a plurality of RSUs use thesame BSSID.

Embodiments of the present disclosure further provide a service in awireless communication system supporting a V2I scheme based on at leastone of location information of at least one RSU and location informationof a vehicle, and for decreasing RSUs to be scanned.

Aspects of the present disclosure may also be embodied as computerreadable code on a non-transitory computer readable recording medium. Anon-transitory computer readable recording medium is any data storagedevice that can store data, which can be thereafter read by a computersystem. Examples of the non-transitory computer readable recordingmedium include read only memory (ROM), random access memory (RAM),CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, anddata transmission through the Internet. The non-transitory computerreadable recording medium can also be distributed over network coupledcomputer systems so that the computer readable code is stored andexecuted in a distributed fashion. In addition, functional programs,code, and code segments for accomplishing the present disclosure can beeasily construed by programmers skilled in the art to which the presentdisclosure pertains.

It can be appreciated that a method and apparatus according to anembodiment of the present disclosure may be implemented by hardware,software and/or a combination thereof. The software may be stored in anon-volatile storage including but not limited to an erasable orre-writable ROM, a memory a RAM, a memory chip, a memory device, or amemory integrated circuit (IC), or an optically or magneticallyrecordable non-transitory machine-readable or computer-readable storagemedium, such as a compact disk (CD), a digital video disc (DVD), amagnetic disk, or a magnetic tape. A method and apparatus according toan embodiment of the present disclosure may be implemented by a computeror a mobile terminal that includes a controller and a memory, and thememory may be an example of a non-transitory machine-readable orcomputer-readable storage medium suitable to store a program or programsincluding instructions for implementing embodiments of the presentdisclosure.

The present disclosure may include a program including code forimplementing the apparatus and method as defined by the appended claims,and a non-transitory machine-readable or computer-readable storagemedium storing the program. The program may be electronicallytransferred via any media, such as communication signals, which aretransmitted through wired and/or wireless connections, and the presentdisclosure may include their equivalents.

An apparatus according to an embodiment of the present disclosure mayreceive the program from a program providing device which is connectedto the apparatus via a wire or a wireless and store the program. Theprogram providing device may include a memory for storing instructionswhich instruct to perform a content protect method which has beenalready installed, information necessary for the content protect method,a communication unit for performing a wired or a wireless communicationwith a graphic processing device, and a controller for transmitting arelated program to a transmitting/receiving device based on a request ofthe graphic processing device or automatically transmitting the relatedprogram to the transmitting/receiving device.

While the present disclosure has been shown and described with referenceto embodiments thereof, it will be understood by those skilled in theart that various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. An access point (AP) in a wireless communicationsystem supporting a vehicle to infrastructure (V2I) scheme, the APcomprising: a controller configured to generate a neighbor APinformation message including location information of each of neighborAPs; and a transmitter configured to transmit the neighbor APinformation message, wherein the neighbor AP information messageincludes a field indicating that a type of a currently transmittedmessage includes location information, a length field indicating alength of fields located after the length field in the currentlytransmitted message, and a location information field indicatinglocation information of each of the neighbor APs.
 2. The AP of claim 1,wherein the location information field includes a location valuesub-field including at least one of latitude information and longitudeinformation of one of the neighbor APs.
 3. The AP of claim 2, whereinthe location information field includes a length sub-field indicating alength of a sub-field located after the length sub-field.
 4. A station(STA) in a wireless communication system supporting a vehicle toinfrastructure (V2I) scheme, the STA comprising: a controller configuredto generate a neighbor access point (AP) information request messageincluding location information of the STA; and a transmitter configuredto transmit the neighbor AP information request message to an AP,wherein the neighbor AP information request message includes a fieldindicating that a type of a currently transmitted message includeslocation information, a length field indicating a length of fieldslocated after the length field in the currently transmitted message, anda location information field indicating location information of the STA.5. The STA of claim 4, wherein the location information field includes alength sub-field indicating a length of a sub-field located after thelength sub-field, and a location value sub-field including at least oneof latitude information and longitude information of the STA.
 6. The STAof claim 4, wherein the neighbor AP information request message furtherincludes at least one of direction information indicating a movingdirection of the STA and speed information indicating a speed of theSTA.
 7. A station (STA) in a wireless communication system supporting avehicle to infrastructure (V2I) scheme, the STA comprising: a controllerconfigured to generate a neighbor access point (AP) information requestmessage including location information of the STA; and a transmitterconfigured to transmit the neighbor AP information request message to anAP, wherein the neighbor AP information request message includes anidentifier indicating that a currently transmitted message requestsneighbor AP information, a length field indicating a length of fieldslocated after the length field in the currently transmitted message, anda location information field indicating location information of the STA.8. The STA of claim 7, wherein the location information field includesat least one of latitude information and longitude information of theSTA.
 9. The STA of claim 7, wherein the neighbor AP information requestmessage further includes at least one of direction informationindicating a moving direction of the STA and speed informationindicating a speed of the STA.
 10. A station (STA) in a wirelesscommunication system supporting a vehicle to infrastructure (V2I)scheme, the STA comprising: a transmitter; a receiver configured toreceive a neighbor access point (AP) information message includinglocation information of neighbor APs from an AP; and a controllerconfigure to select neighbor APs to be scanned by the STA among theneighbor APs based on the location information of the neighbor APs,wherein the transmitter and the receiver are configured to perform ascan process on the selected neighbor APs, and wherein the neighbor APinformation message includes a field indicating that a type of acurrently transmitted message includes location information, a lengthfield indicating a length of fields located after the length field inthe currently transmitted message, and a location information fieldindicating location information of each of the neighbor APs.
 11. The STAof claim 10, wherein the location information field includes a locationvalue sub-field including at least one of latitude information andlongitude information of one of the neighbor APs.
 12. The STA of claim11, wherein the location information field includes a length sub-fieldindicating a length of a sub-field located after the length sub-field.13. The STA of claim 10, wherein the transmitter is configured totransmit a neighbor AP information request message to the AP, andwherein the neighbor AP information request message includes a fieldindicating that a type of a currently transmitted message includeslocation information, a length field indicating a length of fieldslocated after the length field in the currently transmitted message, anda location information field indicating location information of the STA.